In milling in certain types of materials, at times problems arise in the form of regenerative vibrations. This phenomenon is particularly common when the milling tools are long or slender and the material (e.g., titanium) difficult to machine. Under unfavorable circumstances, the vibrations may cause great damage not only in the milling cutter and/or the workpiece, but also in the machine and its surroundings. A well-tried way to try to manage the vibration problems is to use milling cutters having a differential pitch, i.e., tools the milling inserts of which are unevenly distributed along the periphery of the milling cutter body. In such a way, initial tendencies to the emergence of vibrations can in many cases be extinguished before they have time to be fed back and built up to harmful amplitudes.
Previously known milling cutters of the type that has differentially pitched milling inserts have, however, limitations, more precisely as a consequence of the pitch between the milling inserts being invariable or fixed by the fact that the same is determined by the mutual placement of the seats or insert seats in which the milling inserts are mounted. This placement is established once and for all in connection with the manufacture of the milling cutter body and cannot be altered after that. However, the emergence of vibrations is dependent upon a number of complex factors difficult to predict, such as the dynamics of machine—tool and workpiece. Therefore, under unfavorable circumstances, the differential pitch in question may be inappropriate or unfit for the task of counteracting regenerative vibrations. A provisional measure to avoid harmful vibrations in the last-mentioned case—if possible—is to take away one or more milling inserts in order to, in such a way, alter the pitch between these and reduce the feedback. However, this leads to the feed speed, and thereby the productivity of the milling cutter, having to be reduced. Another provisional measure is to decrease the cutting depth, something which however also entails a reduced productivity.
The present invention aims at obviating the above-mentioned disadvantages of previously known milling cutters and at providing an improved milling cutter. Therefore, a primary object of the invention is to provide a milling cutter, the pitch of which between the active cutting edges of the milling inserts can, if required, be altered quickly and easily without the cutting depth or the number of milling inserts needing to be reduced, i.e., without any provisional, productivity deteriorating measures needing to be resorted to.